Conventionally, throttle devices of the above type includes those disclosed in, for example, JP 55-44149 A (Patent Literature 1), JP 55-44150 A (Patent Literature 2), and JP 59-25756 U (Patent Literature 3).
The above conventional throttle devices include a differential pressure type expansion valve, where a valve opening level varies according to a differential pressure between a pressure of a refrigerant on a condenser side (primary side) and a pressure of the refrigerant on an evaporator side (secondary side) and have a coil spring (spring) to energize a valve body in a valve closing direction against a force generated by this differential pressure. Valve opening level characteristics are specified according to this differential pressure and a spring constant of the coil spring.